package network;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User:24097
 * Date:2025-10-11
 * Time:21:24
 */
public class UdpEchoServer {
    private DatagramSocket socket=null;

    public UdpEchoServer(int port) throws SocketException {
        socket=new DatagramSocket(port);
    }

    public void start() throws IOException {
        System.out.println("服务器启动");
        while (true){
             //1.读取
            DatagramPacket requestPacket=new DatagramPacket(new byte[4096],4096);
            socket.receive(requestPacket);
            //读取二进制数据，转换成字符，只构造有效部分
            String request=new String(requestPacket.getData(),0,requestPacket.getLength());
            //2.响应
            //此处是回显服务器
            String response=process(request);
            //3.返回
            //根据response构造DatagramPacker,发送给客户端.
            DatagramPacket responsePacket=new DatagramPacket(response.getBytes(),response.getBytes().length,
                    requestPacket.getSocketAddress());
            //此处还不能直接发送，因为UDP协议自身没有保存对方的信息
            //需要指定目的ip和目的端口.
            socket.send(requestPacket);
            //4.打印日志
            System.out.printf("[%s:%d] req: %s, resp: %s\n",requestPacket.getAddress().toString(),
                    requestPacket.getPort(), request,response);
        }
    }
    public String process(String request){
        return request;
    }

    public static void main(String[] args) throws IOException {
        UdpEchoServer server=new UdpEchoServer(9090);
        server.start();
    }
}
